1. Technical Field
The inventive concept relates to a variable resistance memory device and a method of manufacturing the same, and more particularly, to a variable resistance memory device and a method of manufacturing the same using a transistor as an access device.
2. Related Art
Nonvolatile memory devices have characteristics that data stored therein is not erased even in power off and thus the nonvolatile memory devices have been widely adopted by computers, mobile telecommunication systems, memory cards, and the like.
Flash memory devices have typically been widely used as the nonvolatile memory devices. The flash memory devices typically have memory cells having a stack gate structure. To improve reliability and program efficiency in the flash memory devices, film quality of a tunnel oxide layer has to be improved and a coupling ratio of a cell has to be increased.
Currently, next-generation memory devices, for example, phase-change random access memories (PCRAMs), resistance RAMs (ReRAMs), and magentoresistive RAMs (MRAMs) have been suggested.
As typical next-generation memory devices, PCRAMs need an access device configured to selectively provide current to a phase-change resistance layer. Currently, transistors and diodes are mainly used as the access device in the PCRAMs.
However, the transistors have a low threshold voltage, but the transistors occupy a relatively larger area than the diodes. While the diodes occupy a smaller area than the transistors, the diodes have a larger threshold voltage than the transistors. Further, if the diodes are arranged over a word line, then word line bouncing may be caused due to a resistance difference of the word line according to an arrangement position of the diodes.